High-performance self-driven ultraviolet photodetectors based on lead-free ferroelectric/semiconductor epitaxial heterojunctions

Lead‑free ferroelectric/semiconductor heterojunctions offer a promising route toward high‑performance self‑powered ultraviolet (UV) photodetectors, yet simultaneously achieving high responsivity (R) and detectivity (D*) remains challenging. In this work, a (K0.44Na0.52Li0.04)(Nb0.86Sb0.04Ta0.10)O3 (KNLNST)/Nb‑doped SrTiO3 epitaxial heterojunction photodetector was fabricated via pulsed laser deposition. The device exhibits remarkable photodetection performance modulated by ferroelectric polarization. Compared to the device in an unpoled state (R = 23.5 mA/W, D* = 6.4×1011 Jones), it shows significantly improved performance (R = 25.5 mA/W, D* = 7.0×1011 Jones) in upward poling state and degraded performance (R = 22.3 mA/W, D* = 6.1×1011 Jones) in downward poling state. Under weak light illumination (4 mW/cm2), the photodetector achieves a responsivity of 54.6 mA/W and a detectivity of 1.33 × 1012 Jones with fast rise/decay response times of 141/105 ms. Under a +5 V bias voltage, the device exhibits a responsivity of 5.21 A/W and a detectivity of 1.78×1012 Jones, enabling versatile dual-mode operation for diverse application scenarios. These results demonstrate that epitaxial lead‑free ferroelectric heterojunctions provide an effective strategy for developing high‑performance, self‑driven UV photodetectors.